// Copyright (C) 2024 Kumo inc.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
#pragma once

#include <cassert>
#include <turbo/base/macros.h>

#ifndef NDEBUG

#include <turbo/log/logging.h>

#endif

#include <turbo/threading/thread_collision_warner.h>

namespace turbo {

    namespace subtle {

        class TURBO_EXPORT RefCountedBase {
        public:
            bool HasOneRef() const { return ref_count_ == 1; }

        protected:
            RefCountedBase()
                    : ref_count_(0), in_dtor_(false) {
            }

            ~RefCountedBase() {
#ifndef NDEBUG
                DKCHECK(in_dtor_) << "RefCounted object deleted without calling Release()";
#endif
            }


            void AddRef() const {
                // TODO(maruel): Add back once it doesn't assert 500 times/sec.
                // Current thread books the critical section "AddRelease"
                // without release it.
                // DFAKE_SCOPED_LOCK_THREAD_LOCKED(add_release_);
#ifndef NDEBUG
                DKCHECK(!in_dtor_);
#endif
                ++ref_count_;
            }

            // Returns true if the object should self-delete.
            bool Release() const {
                // TODO(maruel): Add back once it doesn't assert 500 times/sec.
                // Current thread books the critical section "AddRelease"
                // without release it.
                // DFAKE_SCOPED_LOCK_THREAD_LOCKED(add_release_);
#ifndef NDEBUG
                DKCHECK(!in_dtor_);
#endif
                if (--ref_count_ == 0) {
#ifndef NDEBUG
                    in_dtor_ = true;
#endif
                    return true;
                }
                return false;
            }

        private:
            mutable int ref_count_;
#if defined(__clang__)
            mutable bool ALLOW_UNUSED  in_dtor_;
#else
            mutable bool in_dtor_;
#endif
            DFAKE_MUTEX(add_release_);

            TURBO_DISALLOW_COPY_AND_ASSIGN(RefCountedBase);
        };

        class TURBO_EXPORT RefCountedThreadSafeBase {
        public:
            bool HasOneRef() const;

        protected:
            RefCountedThreadSafeBase();

            ~RefCountedThreadSafeBase();

            void AddRef() const;

            // Returns true if the object should self-delete.
            bool Release() const;

        private:
            mutable std::atomic<int32_t> ref_count_;
#if defined(__clang__)
            mutable bool ALLOW_UNUSED  in_dtor_;
#else
            mutable bool in_dtor_;
#endif

            TURBO_DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafeBase);
        };

    }  // namespace subtle

//
// A base class for reference counted classes.  Otherwise, known as a cheap
// knock-off of WebKit's RefCounted<T> class.  To use this guy just extend your
// class from it like so:
//
//   class MyFoo : public turbo::RefCounted<MyFoo> {
//    ...
//    private:
//     friend class turbo::RefCounted<MyFoo>;
//     ~MyFoo();
//   };
//
// You should always make your destructor private, to avoid any code deleting
// the object accidently while there are references to it.
    template<class T>
    class RefCounted : public subtle::RefCountedBase {
    public:
        RefCounted() {}

        void AddRef() const {
            subtle::RefCountedBase::AddRef();
        }

        void Release() const {
            if (subtle::RefCountedBase::Release()) {
                delete static_cast<const T *>(this);
            }
        }

    protected:
        ~RefCounted() {}

    private:
        TURBO_DISALLOW_COPY_AND_ASSIGN(RefCounted);
    };

// Forward declaration.
    template<class T, typename Traits>
    class RefCountedThreadSafe;

// Default traits for RefCountedThreadSafe<T>.  Deletes the object when its ref
// count reaches 0.  Overload to delete it on a different thread etc.
    template<typename T>
    struct DefaultRefCountedThreadSafeTraits {
        static void Destruct(const T *x) {
            // Delete through RefCountedThreadSafe to make child classes only need to be
            // friend with RefCountedThreadSafe instead of this struct, which is an
            // implementation detail.
            RefCountedThreadSafe<T,
                    DefaultRefCountedThreadSafeTraits>::DeleteInternal(x);
        }
    };

//
// A thread-safe variant of RefCounted<T>
//
//   class MyFoo : public turbo::RefCountedThreadSafe<MyFoo> {
//    ...
//   };
//
// If you're using the default trait, then you should add compile time
// asserts that no one else is deleting your object.  i.e.
//    private:
//     friend class turbo::RefCountedThreadSafe<MyFoo>;
//     ~MyFoo();
    template<class T, typename Traits = DefaultRefCountedThreadSafeTraits<T> >
    class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {
    public:
        RefCountedThreadSafe() {}

        void AddRef() const {
            subtle::RefCountedThreadSafeBase::AddRef();
        }

        void Release() const {
            if (subtle::RefCountedThreadSafeBase::Release()) {
                Traits::Destruct(static_cast<const T *>(this));
            }
        }

    protected:
        ~RefCountedThreadSafe() {}

    private:
        friend struct DefaultRefCountedThreadSafeTraits<T>;

        static void DeleteInternal(const T *x) { delete x; }

        TURBO_DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafe);
    };

//
// A thread-safe wrapper for some piece of data so we can place other
// things in scoped_refptrs<>.
//
    template<typename T>
    class RefCountedData
            : public turbo::RefCountedThreadSafe<turbo::RefCountedData<T> > {
    public:
        RefCountedData() : data() {}

        RefCountedData(const T &in_value) : data(in_value) {}

        T data;

    private:
        friend class turbo::RefCountedThreadSafe<turbo::RefCountedData<T> >;

        ~RefCountedData() {}
    };

}  // namespace turbo

//
// A smart pointer class for reference counted objects.  Use this class instead
// of calling AddRef and Release manually on a reference counted object to
// avoid common memory leaks caused by forgetting to Release an object
// reference.  Sample usage:
//
//   class MyFoo : public RefCounted<MyFoo> {
//    ...
//   };
//
//   void some_function() {
//     scoped_refptr<MyFoo> foo = new MyFoo();
//     foo->Method(param);
//     // |foo| is released when this function returns
//   }
//
//   void some_other_function() {
//     scoped_refptr<MyFoo> foo = new MyFoo();
//     ...
//     foo = nullptr;  // explicitly releases |foo|
//     ...
//     if (foo)
//       foo->Method(param);
//   }
//
// The above examples show how scoped_refptr<T> acts like a pointer to T.
// Given two scoped_refptr<T> classes, it is also possible to exchange
// references between the two objects, like so:
//
//   {
//     scoped_refptr<MyFoo> a = new MyFoo();
//     scoped_refptr<MyFoo> b;
//
//     b.swap(a);
//     // now, |b| references the MyFoo object, and |a| references nullptr.
//   }
//
// To make both |a| and |b| in the above example reference the same MyFoo
// object, simply use the assignment operator:
//
//   {
//     scoped_refptr<MyFoo> a = new MyFoo();
//     scoped_refptr<MyFoo> b;
//
//     b = a;
//     // now, |a| and |b| each own a reference to the same MyFoo object.
//   }
//
template<class T>
class scoped_refptr {
public:
    typedef T element_type;

    scoped_refptr() : ptr_(nullptr) {
    }

    scoped_refptr(T *p) : ptr_(p) {
        if (ptr_)
            ptr_->AddRef();
    }

    scoped_refptr(const scoped_refptr<T> &r) : ptr_(r.ptr_) {
        if (ptr_)
            ptr_->AddRef();
    }

    template<typename U>
    scoped_refptr(const scoped_refptr<U> &r) : ptr_(r.get()) {
        if (ptr_)
            ptr_->AddRef();
    }

    scoped_refptr(scoped_refptr<T> &&r) noexcept {
        ptr_ = r.ptr_;
        r.ptr_ = nullptr;
    }

    template<typename U>
    scoped_refptr(scoped_refptr<U> &&r) noexcept {
        ptr_ = r.ptr_;
        r.ptr_ = nullptr;
    }

    ~scoped_refptr() {
        if (ptr_)
            ptr_->Release();
    }

    T *get() const { return ptr_; }

    // Allow scoped_refptr<C> to be used in boolean expression
    // and comparison operations.
    operator T *() const { return ptr_; }

    T *operator->() const {
        assert(ptr_ != nullptr);
        return ptr_;
    }

    scoped_refptr<T> &operator=(T *p) {
        // AddRef first so that self assignment should work
        if (p)
            p->AddRef();
        T *old_ptr = ptr_;
        ptr_ = p;
        if (old_ptr)
            old_ptr->Release();
        return *this;
    }

    scoped_refptr<T> &operator=(const scoped_refptr<T> &r) {
        return *this = r.ptr_;
    }

    template<typename U>
    scoped_refptr<T> &operator=(const scoped_refptr<U> &r) {
        return *this = r.get();
    }

    void swap(T **pp) {
        T *p = ptr_;
        ptr_ = *pp;
        *pp = p;
    }

    void swap(scoped_refptr<T> &r) {
        swap(&r.ptr_);
    }

    // Release ownership of ptr_, keeping its reference counter unchanged.
    T *release() WARN_UNUSED_RESULT {
        T *saved_ptr = nullptr;
        swap(&saved_ptr);
        return saved_ptr;
    }

protected:
    T *ptr_;
};

// Handy utility for creating a scoped_refptr<T> out of a T* explicitly without
// having to retype all the template arguments
template<typename T>
scoped_refptr<T> make_scoped_refptr(T *t) {
    return scoped_refptr<T>(t);
}
